<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<script type="text/javascript"> 
	
	function showCity(){
		//维护一个二维数组存储省份对应的城市
		var citys = [[],["广州","佛山","湛江","中山"],["长沙","衡阳","岳阳","郴州"],["南宁","桂林","贵港","柳州"]];			
	
		//获取省份对应的节点
		var provinceNode = document.getElementById("province");
		//获取省份选中的选项
		var selectIndex =  provinceNode.selectedIndex;
		//获取对应的城市
		var  cityDatas = citys[selectIndex];
		
		//找到city节点
		var cityNode = document.getElementById("city");
		
		/*
		//先清空city框所有option
		var children = cityNode.childNodes;
		for(var i = 0; i<children.length ; ){
			cityNode.removeChild(children[i]);
		}
		*/
		
		//设置options的个数。
		cityNode.options.length = 1 ;
		
		
		
		//遍历对应的所有城市然后创建对应的option添加到city上。
		for(var index = 0; index<cityDatas.length ; index++){
			var option = document.createElement("option");
			option.innerHTML = cityDatas[index];
			cityNode.appendChild(option);
		}
		
		
	
	}
	
</script>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>无标题文档</title>
</head>
<body>
	省份<select id="province" onchange="showCity()">
    		<option>省份</option>
    		<option>广东</option>
            <option>湖南</option>
            <option>广西</option>
    	</select>
	城市<select id="city"><option>城市</option></select>
    
</body>
</html>
